Verma, H.K. and Goel, R.K. and Prasad, V.V.R. (2013) Assessment and Mitigation of Blast Induced Vibration and Overbreak in Kol Dam Hydroelectric Power Project, India – A Case Study. Journal of Rock Mechanics and Tunnelling Technology , 19 (1). pp. 47-59. ISSN 0971-9059

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Abstract

Pre-splitting is the commonly used controlled blasting technique for perimeter control in mining and construction industry. Overbreak and damage to the final slope of excavation adversely affect safety as well as economics of the project. Apart from unsafe slope at the perimeter of rock excavation, pre-split blasting techniques prevents extra cost of rock excavation, backfill material and rock reinforcement. This technique has several advantages such as minimum damage from back-break, enhanced carrying capacity of rock, higher structural stability and stable final pit walls or slope at the designed angle thus improving overall safety of wall / slope. This paper presents a case study of Kol dam hydroelectric power project (KHEPP). This 800 MW project is under construction on river Satluj in Himalaya, India. The excavation in the project consists of preparation of seven benches having slope of 1:4 starting from elevation level (EL) 715.0 m to EL 618.0 m in the approach channel area, each bench having height 15 m and berm width of 5 m. Three sets of joints in the two dominant rock types of approach channel area namely pink limestone and yellowish dolomite, posed geological challenges for the safe excavation. Spacing of the these parallel joints ranges from 0.30 m to 2m. The rock is intensely folded in some parts and shear zones are also present in this area. The joint set in limestone and dolomite made whole rock formation in a block s ize ranging from as small as 0.5 m2 t o a s l arge as 5 .0 m 2. The block formation was prone to overbreak leading to unstable slope. Apart from the geological challenges, the domestic houses close to excavation area are also susceptible to damage due to possible high level of blast induced ground vibration. In all such situations, pre-splitting was carried out in a controlled manner. The blast design gave good result with minimum overbreak and vibration less than 10 mm/s. The technique helped in preparation of the stable slope in the benches as per the required profile and also prevented damages to the domestic structures. This paper gives details of site specific technical challenges and details of the blast design, details of an in arrangement for maintaining drilling accuracy and the techniques evolved for preventing structural damages induced by blast vibrations.

Item Type:	Article
Uncontrolled Keywords:	Controlled blasting technique; Pre-splitting; Ground Vibration; Half cast factor
Subjects:	Blasting
Divisions:	UNSPECIFIED
Depositing User:	Mr. B. R. Panduranga
Date Deposited:	13 Jan 2020 05:56
Last Modified:	13 Jan 2020 05:56
URI:	http://cimfr.csircentral.net/id/eprint/2142

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